The invention relates to a method for correcting deviations in a production process of an article. Using the method, an extended graphical representation and manipulation of deviations may be effectuated in 3D coordinate metrology.
Currently, CAD models are usually presented on screens or printouts in a 2D or 3D representation. As a rule, the deviations from the intended contour are represented as deviation vectors or by means of colored areas. By way of example, this is known from https://jgarantmc.com/part-to-cad-comparison/.
If the deviations should be prepared for correction purposes, use is made, as a rule, of pointer devices such as a mouse, a trackpad or a touchscreen in order to define the desired manipulations, for example, the selection of correction regions. Since the pointer devices lack the third dimension, swift work on multiply curved surfaces is often impossible.
By way of example, provision is made in EP 2788714 A1 of a camera in a coordinate measuring machine (also abbreviated CMM below), the camera recording an image of an object. The image is used for forming a point cloud with 3D positions of target points of an object. The camera can be combined with a 3D display, for example virtual reality goggles, or a 3D touchscreen, on which the point cloud is presented. On the 3D touchscreen, a user can select points on the surface of the object that are to be measured using the CMM. However, the problem specified above is not solved thereby.
Industrial metrology is an essential constituent part of the production of workpieces. Quality assurance is also imperative according to the ISO 9000 standards in order to make products commercially available. The measurement process in industrial metrology is already a process chain per se. The actual surface of a manufactured workpiece is ascertained point-by-point with the aid of a measuring machine (in particular a CMM), a controller, a computer and the appropriate software. The coordinates of the surface points are determined by mechanical sensing using special sensors or by imaging methods. The set of actual data in the form of X-, Y-, Z-coordinates obtained in the first step is not suitable for making a statement about the quality of the workpiece. The quality of a workpiece is specified by intended dimensions and the associated tolerances. The measurement process is increasingly carried out directly in the manufacturing surroundings so that, where possible, no rejects are even produced. In the case of simple problems, for example checking a diameter, it is possible to automatically make a good/bad decision. In the case of complex parts with free-form surfaces, such as e.g. in the case of a turbine blade, a human must carry out an evaluation as soon as there is indication for a tolerance being exceeded. Depending on size, a turbine blade may cost several ten thousand Euro. Therefore, a decision is made case-by-case as to whether this is a reject, whether post-processing is possible or whether a concession can be made. The decisions are made by certified members of staff. However, it is difficult here to quickly make a correct decision.
The object of the invention consists of specifying a solution to the problems mentioned above.